Memory is the ability to remember the past in a conscious or unconscious state, and since learning and memory are closely connected with each other, especially, they should be always considered together.
The memory is divided into unconscious non-declarative memory including acquirement of techniques, habits, and so on and declarative memory including facts or events in the past, which can be reproduced consciously.
If complicate activities like driving, playing the piano, and the like become habituated, however, they can be carried out unconsciously, and through the repeated activities, therefore, the declarative memory can be converted into the non-declarative memory.
The declarative memory is classified into working memory collected to information given at the moment to allow the information to be temporarily stored only for several seconds, short-term memory kept for several hours to days, and remote memory capable of remembering past experiences a long time ago.
The short-term memory includes a term in which the memory on the event currently occurring is converted into the remote memory. During the term, the event is hard to be stored as memory and is easily forgotten, but only if the event is stored as the remote memory, it is not easily forgotten even in a case where serious injury happens to the brain.
As social environments are diversified, on the other hand, people are exposed to a lot of stimuli so that rapid brain activities are required to receive such stimuli.
Particularly, environment destruction, water pollution, and overflow of instant foods, which are caused by economic growth and industrialization, threaten health of people, and over-nutrition of meat eating caused by income increase and absolute lack of exercise caused by the development of machines accelerate obesity of people. Due to the obesity, further, chronic degenerative adult diseases such as arteriosclerosis, hypertension, coronary heart diseases, myocardial infarction, angina pectoris, cerebral infarction, and the like have been prevailed.
Also, patients with Alzheimer-type dementia have been increased every year. Further, the youth, especially, examinees feel fatigued in brain, mind and body because of their learning activity for long term, and such fatigue gives serious influences on healthy development of brain.
As the society is complicated and college entrance examination competition is fierce, accordingly, there is a definite need for developing a method for cleaning brain to promote memory and to accelerate fatigue recovery.
So as to satisfy such need, up to now, there have been proposed various treatments and conditions related to memory for the purpose of memory disorder treatment, memory promotion, or brain function activation.
For example, it is suggested that memory disorders are connected with aging process or neurodegenerative diseases like Alzheimer's disease and also memory deficits happen after brain injury or multi-infarct dementia.
Many chemical compounds and treatment methods have been studied to improve perception, that is, to promote memory and to store the memory for long term. As compounds useful in promotion of memory and treatment of memory disorders, for example, Milacemide (U.S. Pat. No. 4,639,468) have been developed.
Further, as a treatment method for various memory disorders like Alzheimer's disease having decreased cholinergic nerve functions, acethylcholin esterase inhibitor is used to increase contents of acethylcholin.
Also, a specific 9-amino-tetrahydroacridine derivative has an effect of inhibiting acethylcholin esterase so that it is effective in treatment of Alzheimer's disease (Japanese Patent Nos. S61-148154, S63-141980, S63-166881, S63-203664, S63-225358, S63-238063 and S63-239271, European Patent No. EP0268871A1, and International Patent No. WO88/02256).
However, the treatment for the Alzheimer's disease is not sufficiently achieved with the above-mentioned methods, and also, additional processes have to be required to produce the compounds massively. If the compounds are applied to the living body, toxicity may be generated from the compounds.
So as to overcome such problems, up to now, medicines or functional health foods to which prescription for oriental medicine is partially applied have been developed to achieve memory promotion and brain function activation.
The most representatively emerging food is Panax ginseng C.A. Meyer among them, and up to now, many studies have been made on the effects of ginseng on brain activities like learning, memory, and so on.
In addition to ginseng, blue-backed fish, especially, head of tuna contains a large amount of docosahexaenoic acid (DHA), and recently, it is widely known that the DHA is important for the development of the brain, which becomes a global issue. Accordingly, many studies on the DHA have been made.
According to the study, the DHA has a memory and learning control function through memory and learning tests and is very effective in prevention of Alzheimer-type dementia. However, it is known that the DHA is important for the development of the brain only in infants and gives no influence on the development of the brain or the improvement of memory in growing children or adults. Above all, the DHA has to be extracted from tuna, and even if it is artificially synthesized, an appropriate process for mass production has to be required, which raises a manufacturing cost and undesirably giving no economical advantages.
Under the above-mentioned situation, there is a need for the development of desirable natural medicines having effects on the promotion of memory and learning ability to which much attention in modern societies is paid, and especially, there is a definite need for the development of a functional health food which is prepared with non-toxic and economical natural components, thereby being contributed to the industrialization of natural resources and being easily accessed to demanders.